1. Field of the Invention
The present invention relates to a water-disintegratable fibrous sheet that can be easily dispersed by a water stream. More particularly, the invention relates to a water-disintegratable fibrous sheet excellent in water-disintegratability and strength, and a water-disintegratable wiping sheet comprising a plurality of the water-disintegratable fibrous sheets laminated with each other.
2. Description of the Prior Art
Fibrous sheets are used for cleansing human skin, e.g., skin around anus, or cleaning a toilet room. The fibrous sheet is preferably water-disintegratable to be thrown away and drained in a toilet as it is. If it is not excellent in water-disintegratability, it requires a long time to be dispersed in a septic tank, and brings danger of clogging drainpipes of a toilet, when being thrown away and drained in a toilet. However, in general, a packed fibrous sheet impregnated with a cleansing liquid or the like has to be strong enough to endure conducting wiping operations while being impregnated with a cleansing liquid, and at the same time, has to keep water-disintegratability in the event of being thrown away and drained in a toilet. Therefore, a water-disintegratable fibrous sheet that has good water-disintegratability and strength sufficient to use is demanded.
Unexamined Published Japanese Patent Application No. H1-168999 discloses an easily water-dispersible cleaning product containing water-insoluble carboxymethylated pulp in a salt form of calcium. Unexamined Published Japanese Patent Applications No. H9-132896 and No. H9-132897 each discloses a water-disintegratable sheet, in which sodium carbonate is added to water-insoluble or water-swellable carboxymethyl cellulose. However, when a large amount of the binder, i.e., water-insoluble or water-swellable carboxymethylated pulp, is used to enhance sheet strength, water-disintegratability of the sheet is deteriorated.